var hexcase = 0; /* hex output format. 0 - lowercase; 1 - uppercase */ 
var chrsz = 8; /* bits per input character. 8 - ASCII; 16 - Unicode */ 
       
       function sha1(s){
    
            return binb2hex(core_sha1(AlignSHA1(s)));
    
        }
    
    
    
        /*
         *
         * Calculate the SHA-1 of an array of big-endian words, and a bit length
         *
         */
        function core_sha1(blockArray){
    
            var x = blockArray; // append padding
            var w = Array(80);
    
            var a = 1732584193;
    
            var b = -271733879;
    
            var c = -1732584194;
    
            var d = 271733878;
    
            var e = -1009589776;
    
            for (var i = 0; i < x.length; i += 16) // 每次处理512位 16*32
            {
    
                var olda = a;
    
                var oldb = b;
    
                var oldc = c;
    
                var oldd = d;
    
                var olde = e;
    
                for (var j = 0; j < 80; j++) // 对每个512位进行80步操作
                {
    
                    if (j < 16) 
                        w[j] = x[i + j];
    
                    else
                        w[j] = rol(w[j - 3] ^ w[j - 8] ^ w[j - 14] ^ w[j - 16], 1);
    
                    var t = safe_add(safe_add(rol(a, 5), sha1_ft(j, b, c, d)), safe_add(safe_add(e, w[j]), sha1_kt(j)));
    
                    e = d;
    
                    d = c;
    
                    c = rol(b, 30);
    
                    b = a;
    
                    a = t;
    
                }
    
                a = safe_add(a, olda);
    
                b = safe_add(b, oldb);
    
                c = safe_add(c, oldc);
    
                d = safe_add(d, oldd);
    
                e = safe_add(e, olde);
    
            }
    
            return new Array(a, b, c, d, e);
    
        }
    
        /*
         *
         * Perform the appropriate triplet combination function for the current
         * iteration
         *
         * 返回对应F函数的值
         *
         */
        function sha1_ft(t, b, c, d){
    
            if (t < 20) 
                return (b & c) | ((~ b) & d);
    
            if (t < 40) 
                return b ^ c ^ d;
    
            if (t < 60) 
                return (b & c) | (b & d) | (c & d);
    
            return b ^ c ^ d; // t<80
        }
    
        /*
         *
         * Determine the appropriate additive constant for the current iteration
         *
         * 返回对应的Kt值
         *
         */
        function sha1_kt(t){
    
            return (t < 20) ? 1518500249 : (t < 40) ? 1859775393 : (t < 60) ? -1894007588 : -899497514;
    
        }
    
        /*
         *
         * Add integers, wrapping at 2^32. This uses 16-bit operations internally
         *
         * to work around bugs in some JS interpreters.
         *
         * 将32位数拆成高16位和低16位分别进行相加，从而实现 MOD 2^32 的加法
         *
         */
        function safe_add(x, y){
    
            var lsw = (x & 0xFFFF) + (y & 0xFFFF);
    
            var msw = (x >> 16) + (y >> 16) + (lsw >> 16);
    
            return (msw << 16) | (lsw & 0xFFFF);
    
        }
    
        /*
         *
         * Bitwise rotate a 32-bit number to the left.
         *
         * 32位二进制数循环左移
         *
         */
        function rol(num, cnt){
    
            return (num << cnt) | (num >>> (32 - cnt));
    
        }
    
        /*
         *
         * The standard SHA1 needs the input string to fit into a block
         *
         * This function align the input string to meet the requirement
         *
         */
        function AlignSHA1(str){
    
            var nblk = ((str.length + 8) >> 6) + 1, blks = new Array(nblk * 16);
    
            for (var i = 0; i < nblk * 16; i++) 
                blks[i] = 0;
    
            for (i = 0; i < str.length; i++) 
    
                blks[i >> 2] |= str.charCodeAt(i) << (24 - (i & 3) * 8);
    
            blks[i >> 2] |= 0x80 << (24 - (i & 3) * 8);
    
            blks[nblk * 16 - 1] = str.length * 8;
    
            return blks;
    
        }
    
        /*
         *
         * Convert an array of big-endian words to a hex string.
         *
         */
        function binb2hex(binarray){
    
            var hex_tab = hexcase ? "0123456789ABCDEF" : "0123456789abcdef";
    
            var str = "";
    
            for (var i = 0; i < binarray.length * 4; i++) {
    
                str += hex_tab.charAt((binarray[i >> 2] >> ((3 - i % 4) * 8 + 4)) & 0xF) +
    
                hex_tab.charAt((binarray[i >> 2] >> ((3 - i % 4) * 8)) & 0xF);
    
            }
    
            return str;
    
        }
    
        /*
         *
         * Perform a simple self-test to see if the VM is working
         *
         */
        function sha1_vm_test(){
    
            return hex_sha1("abc") == "a9993e364706816aba3e25717850c26c9cd0d89d";
    
        }

        window.sha1 = sha1;